build/ci: green builds and tests on all three platforms

Compiler hygiene (all platforms):
- Silence warnings across the tree: missing override, -Wreorder ctor
  init, -Wshadow, -Wsign-compare, missing switch cases, unused
  functions/captures, Qt 6.11 deprecations (QMouseEvent/QDropEvent
  accessors, qAsConst, Q_FOREACH over non-shared containers,
  AA_UseHighDpiPixmaps) and the .bak/ backup tree removal.
- Fix regressions from the cleanup: missing clip decls in
  capi/timeline.cpp, plugin.cpp rename fallout, panel setFocus
  ambiguity, QGraphicsItem::pos vs event->position(), duplicate
  k_push_button case, boolean test variable.

Windows:
- Qt portability: CommandLineParser is_set/add_option, QTimeZone
  systemTimeZone (QTimeZone::LocalTime is 6.11-only), k_progress_* enum.
- Linking: stop adding oakengine to OLIVE_LIBRARIES (import lib plus
  oakengine-obj caused multiple definitions); add OAKENGINE_STATIC so
  internal consumers no longer reference __imp_* stubs.
- oakengine.ver: export olive::Renderer typeinfo so liboakgl.so can be
  dlopened (Linux), DynamicRenderer no longer dlcloses backend libraries
  (crash in RenderManager's dtor calling into unmapped memory).
- OTIO runtime: copy DLLs next to every binary on Windows instead of
  relying on PATH (0xc0000135 in gtest discovery).
- Headless GL: the runner only has GDI OpenGL 1.1, killing every render
  worker. Deploy Mesa llvmpipe as opengl32sw.dll (Qt's software-GL
  channel) with QT_OPENGL=software, and let QT_OPENGL override the
  AA_UseDesktopOpenGL default. ExportTask fails fast after 8 consecutive
  undelivered frames instead of segfaulting or grinding forever;
  FFmpegEncoder::write_frame tolerates null frames.
- Tests: GetTempPathA+PID temp dirs, GetLongPathNameA for 8.3 names,
  forward-slash normalization when comparing project filenames.

Linux:
- Install libshaderc-dev so oakvulkan compiles GLSL (Vulkan tests).
- Accept UNORM floor-or-round (63/64) in the blit ping-pong test.
- Skip MainWindow construction test on the offscreen QPA (cannot paint
  QOpenGLWidget).

Also: oak_cli_transcode gets a 300s ctest timeout, worker logs GL
context version and LoadGraph/render_frame stages, and
docs/plans/eliminate-event-bridge-issues.md (English translation).

tests/gtest/audio_smoke_test.cpp

@@ -44,7 +44,7 @@ namespace test
 // Helper Functions
 // ============================================================================
 
-static AudioParams make_audio_params(int sample_rate, uint64_t channel_layout,
+[[maybe_unused]] static AudioParams make_audio_params(int sample_rate, uint64_t channel_layout,
 								   SampleFormat format)
 {
 	return AudioParams(sample_rate, channel_layout, format);
@@ -951,7 +951,7 @@ TEST(AudioSmokeThread, ConcurrentWaveformAccess)
 	std::atomic<int> success_count{ 0 };
 
 	for (int t = 0; t < num_threads; ++t) {
-		threads.emplace_back([&waveform, &success_count, num_ops_per_thread]() {
+		threads.emplace_back([&waveform, &success_count]() {
 			for (int i = 0; i < num_ops_per_thread; ++i) {
 				// Read summary from different times
 				auto summary = waveform.get_summary_from_time(

tests/gtest/common_filefunctions_test.cpp

@@ -50,7 +50,7 @@ TEST(CommonFileFunctions, GetSafeTemporaryFilename)
 	EXPECT_TRUE(first.contains(QStringLiteral(".tmp0.")));
 
 	QFile f(first);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.close();
 
 	QString second = olive::FileFunctions::get_safe_temporary_filename(base);
@@ -80,19 +80,19 @@ TEST(CommonFileFunctions, RenameFileAllowOverwrite)
 	QString to = dir.filePath(QStringLiteral("to.txt"));
 
 	QFile f(from);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("source");
 	f.close();
 
 	QFile t(to);
-	t.open(QIODevice::WriteOnly);
+	(void)t.open(QIODevice::WriteOnly);
 	t.write("existing");
 	t.close();
 
 	EXPECT_TRUE(olive::FileFunctions::rename_file_allow_overwrite(from, to));
 	EXPECT_FALSE(QFileInfo::exists(from));
 	QFile result(to);
-	result.open(QIODevice::ReadOnly);
+	(void)result.open(QIODevice::ReadOnly);
 	EXPECT_EQ(result.readAll(), QByteArray("source"));
 }
 
@@ -105,7 +105,7 @@ TEST(CommonFileFunctions, CanCopyDirectoryWithoutOverwriting)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.close();
 
 	EXPECT_TRUE(olive::FileFunctions::can_copy_directory_without_overwriting(
@@ -113,7 +113,7 @@ TEST(CommonFileFunctions, CanCopyDirectoryWithoutOverwriting)
 
 	QString dst_file = QDir(dst.path()).filePath(QStringLiteral("file.txt"));
 	QFile g(dst_file);
-	g.open(QIODevice::WriteOnly);
+	(void)g.open(QIODevice::WriteOnly);
 	g.close();
 
 	EXPECT_FALSE(olive::FileFunctions::can_copy_directory_without_overwriting(
@@ -129,7 +129,7 @@ TEST(CommonFileFunctions, CopyDirectory)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("copied");
 	f.close();
 
@@ -208,20 +208,20 @@ TEST(CommonFileFunctions, CopyDirectoryWithOverwrite)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("new content");
 	f.close();
 
 	QString dst_file = QDir(dst.path()).filePath(QStringLiteral("file.txt"));
 	QFile g(dst_file);
-	g.open(QIODevice::WriteOnly);
+	(void)g.open(QIODevice::WriteOnly);
 	g.write("old content");
 	g.close();
 
 	olive::FileFunctions::copy_directory(src.path(), dst.path(), true);
 
 	QFile result(dst_file);
-	result.open(QIODevice::ReadOnly);
+	(void)result.open(QIODevice::ReadOnly);
 	EXPECT_EQ(result.readAll(), QByteArray("new content"));
 }
 

tests/gtest/dynamic_render_backend_test.cpp

@@ -372,9 +372,11 @@ TEST(DynamicRenderBackend, VulkanIterativeBlitPingPong)
 	QByteArray dst_data(k_size * k_size * 4, 0);
 	dst->download(dst_data.data(), k_size);
 
-	// After two halving passes, red is 255 * 0.5 * 0.5. UNORM conversion floors
-	// the intermediate value, so the result is 63 rather than 64.
-	EXPECT_EQ(static_cast<uint8_t>(dst_data[0]), 63u);
+	// After two halving passes, red is 255 * 0.5 * 0.5. UNORM conversion may
+	// floor (63) or round-to-nearest (64) depending on the driver (llvmpipe
+	// rounds); both are spec-conformant.
+	const uint8_t red = static_cast<uint8_t>(dst_data[0]);
+	EXPECT_TRUE(red == 63u || red == 64u) << "red = " << int(red);
 	EXPECT_EQ(static_cast<uint8_t>(dst_data[1]), 0u);
 	EXPECT_EQ(static_cast<uint8_t>(dst_data[2]), 0u);
 	EXPECT_EQ(static_cast<uint8_t>(dst_data[3]), 255u);

tests/gtest/mainwindow_test.cpp

@@ -3,6 +3,7 @@
 #include <QProgressBar>
 #include <QOffscreenSurface>
 #include <QOpenGLContext>
+#include <QGuiApplication>
 #include <QSignalSpy>
 #include <QTest>
 #include <QXmlStreamReader>
@@ -174,6 +175,14 @@ TEST(MainWindow, ConstructsOffscreenWithPanelsAndMenus)
 	// runners on the offscreen QPA), constructing it crashes in GL code
 	// ("QOpenGLFunctions created with non-current context"). Probe first and
 	// skip where GL is unavailable.
+	// MainWindow instantiates viewer panels containing QOpenGLWidget. The
+	// offscreen QPA cannot paint QOpenGLWidget at all ("QOpenGLWidget is not
+	// supported on this platform") — pumping events then crashes inside Qt's
+	// backing store flush. Skip there regardless of whether a bare
+	// QOpenGLContext can be created.
+	if (QGuiApplication::platformName() == QStringLiteral("offscreen")) {
+		GTEST_SKIP() << "offscreen QPA cannot paint QOpenGLWidget";
+	}
 	QOffscreenSurface probe_surface;
 	probe_surface.create();
 	QOpenGLContext probe_context;

tests/gtest/node_value_extended_test.cpp

@@ -64,8 +64,8 @@ TEST(NodeValueExtended, ColorMatrixBezierAccessors)
 
 TEST(NodeValueExtended, ScalarAccessors)
 {
-	olive::NodeValue boolean(olive::NodeValue::k_boolean, true);
-	EXPECT_TRUE(boolean.to_bool());
+	olive::NodeValue bool_val(olive::NodeValue::k_boolean, true);
+	EXPECT_TRUE(bool_val.to_bool());
 
 	olive::NodeValue floating(olive::NodeValue::k_float, 2.75);
 	EXPECT_DOUBLE_EQ(floating.to_double(), 2.75);

tests/gtest/panel_test.cpp

@@ -138,7 +138,7 @@ inline oak::Project to_oak_project(Project *p)
 }
 
 // The process-wide undo stack previously reached via Core::undo_stack()
-inline UndoStack *app_undo_stack()
+[[maybe_unused]] inline UndoStack *app_undo_stack()
 {
 	return static_cast<UndoStack *>(oakengine_app_undo_stack());
 }

tests/gtest/plugin_smoke_test.cpp

@@ -170,7 +170,7 @@ TEST(PluginSmokeThread, ConcurrentImageAllocation)
 	std::atomic<int> success_count{ 0 };
 
 	for (int t = 0; t < num_threads; ++t) {
-		threads.emplace_back([&success_count, num_allocs_per_thread, t]() {
+		threads.emplace_back([&success_count, t]() {
 			for (int i = 0; i < num_allocs_per_thread; ++i) {
 				OFX::Host::ImageEffect::ClipDescriptor desc(
 					kOfxImageEffectOutputClipName);

tests/gtest/viewer_smoke_test.cpp

@@ -462,7 +462,7 @@ TEST(ViewerSmokeThread, ConcurrentQueueAccess)
 
 	for (int t = 0; t < num_threads; ++t) {
 		threads.emplace_back(
-			[&queue, &append_count, t, num_frames_per_thread]() {
+			[&queue, &append_count, t]() {
 				for (int i = 0; i < num_frames_per_thread; ++i) {
 					ViewerPlaybackFrame frame{
 						Rational(t * num_frames_per_thread + i, 24), QVariant()